As a solid-state light emitting element such as an LED increases in temperature during light emission, its light emitting efficiency and life decrease. Also, some of electronic components of a circuit unit for lighting the solid-state light emitting element are damaged or decrease their life due to thermal effects.
In view of this, there is a need for efficient dissipation of heat generated by the LED and the circuit unit. Patent Literature 1 discloses a light source device including a case composed of a cylindrical body, which is made of a material having excellent thermal conduction properties such as aluminum, whose hollow part is partitioned by a plate member made of the same material as the cylindrical body. The plate member is fixed to the cylindrical body in such a state where an edge part of the plate member is folded back in a predetermined width so as to bring an outer circumferential surface of the folded-back edge part into close contact with an internal circumferential surface of the cylindrical body.
On one of surfaces of the plate member, an LED module is mounted, which is composed of a print substrate on which an LED is mounted. On the other surface of the plate member, a circuit unit is housed in the hollow part of the case.
According to the light source device having the above structure disclosed in the Patent Literature 1, heat generated by the LED module during lighting is dissipated via the plate member and the cylindrical body. On the other hand, heat generated by the circuit unit is conducted to the cylindrical body by radiation, convection within the hollow part, or the like, and then is dissipated from an outer surface of the cylindrical body.